Single-Stream Recycling and the Future of Waste

••• Mark Gibson, Getty Images

单流式回收是一个回收各种可回收物(包括塑料)的系统, paper, metal, and glass) are placed in a single curbside bin by consumers. 然后回收物被收集起来,并运送到一个材料回收设施(MRF),在那里它们被分类和处理. 这个系统也被称为混合或单一分类回收.

A benefit of the single-stream approach is that consumers, or the depositors, don’t have to separate and sort the recyclables themselves. 相反,他们被鼓励把所有不是垃圾的东西都放在一个箱子里. This helps to increase the quantity of material recovered. However, there are also drawbacks to this system, as it's contributed to higher contamination rates, such as mixed cardboard items containing glues and inks.

American Waste

美国环境保护署(EPA)开始收集和报告有关美国废物产生和处置的数据.S. more than 30 years ago. 20世纪90年代,单流回收作为一种低门槛的回收方式在加州的几个社区出现. This trend was slowly adopted by communities across the U.S. 寻找方法来应对塑料和其他包装材料的冲击(例如,2.1996年销售了80亿个塑料水瓶,跃升至42个.6 billion by 2010).

The EPA reports that over time, 城市固体废物(MSW)的回收率从1960年的6%多一点上升到1980年的10%左右, to 16% in 1990, to about 29% in 2000, and to over 35% in 2017. The total MSW recycled in 2017 was 67.200万吨,其中纸张和纸板约占66%. 金属约占12%,而玻璃、塑料和木材约占5%.

For more than 25 years, the U.S. 把大部分的塑料垃圾送到其他国家——尤其是中国——去分解和回收. In 2017, China announced it would no longer accept imports of plastic, textiles, unsorted paper, artificial fibers, various metals, and approximately 20 other types of solid waste. While American demand for plastic continues to grow, 在美国收集和处理清洁可回收材料的未来.S. remains uncertain.

Single-Stream Collection

Once recyclables are put into curbside recycling bins, MRFs collect, sort, and process the recyclables. After processing, 类似种类的可回收物被打包并运往特定材料的回收者, ultimately to be utilized in the production of new products.

实际的分类过程可能会因系统中采用的自动化程度而有所不同, involving technologies such as conveyors, screens, forced air, magnets, optical material identification, and eddy current. 

单流回收对消费者来说是一个简单的过程,但对美国来说代价高昂.S. 回收365App下载手机版,雇佣工人和昂贵的自动化设备来处理垃圾.

The Sorting Process

The process for single-stream recycling is as follows:

  1. All material is unloaded and placed on a conveyor.
  2. Non-recyclable items are manually sorted and removed.
  3. The material moves to a triple-deck screen.
  4. 过重或过轻的物品,如纸板、容器和纸张,应被移走.
  5. 较重的容器会掉到底层,而较轻的物品则会掉到第二层.
  6. 为了工人的安全和方便,一个屏风可以打碎玻璃容器.
  7. 剩下的材料通过一个强大的磁铁来清除锡罐和钢罐.
  8. MRF的工作人员仔细观察那些可能仍在不经意间延续下去的特定商品.
  9. 一种叫做“涡流”的反向磁铁会使铝罐飞离传送带,进入垃圾箱.
  10. MRF的工作人员将硬纸板、新闻纸和办公室用纸分开,并将它们放入下面的掩体中. 一旦所有的材料被分离,它们就被打包并运送到回收公司进行处理.

单流回收的整个过程涉及到机器和人工的结合.

Single-Stream Advantages

单流式回收最显著的优点之一是提高回收率. As individuals or consumers don’t have to do the sorting, 他们更被鼓励参加路边回收项目. Again, less space is required to store collection containers.

Regarding collection, 对于不同的回收流程,拖运过程的成本相对于单独的拾料机降低了, 或者搬运工必须将不同的材料放入不同的车厢. This simple process receives greater public approval.

Single-Stream Disadvantages

单流回收最显著的缺点是,它导致了回收材料的质量下降. 把所有的材料放在一个箱子里会增加污染的可能性,因为碎玻璃和倾向于把未经批准的材料扔进可回收的箱子. 这最终会给MRF运营商和社区带来重大问题.

尽管消费者和存款人并没有自己对这些材料进行分类, someone ultimately has to sort, making the cost of recycling higher.

Looking Toward the Future

有一些正在测试的新工艺,可以减少365App下载手机版目前运输和加工塑料和其他可回收材料的系统的总排放量. IBM公司声称,到2050年,海洋中的塑料将比鱼还要多. 这种令人不安的预测激发了他们最新技术的发展, VolCat:一种催化化学过程,它将某些塑料(称为聚酯)分解成一种物质,然后直接返回塑料制造机器以生产新产品.

"In the coming years, 像VolCat这样的先进技术将使塑料回收更加高效,在处理更多类型的材料方面比之前的技术更加灵活. Unlike traditional mechanical recycling, 未来的塑料回收将会分解彩色和透明塑料, as well as dirty and clean containers, producing a high-quality final product that is 100% recyclable."

While recycling has come a long way in the last decade, 新的技术解决方案能否最大限度地提高消费者的便利性还有待观察, volume recovery, and material quality through a single-stream process.